Added more concrete information on how to contribute.
Added more concrete information on how to contribute.

- Added step by step instructions on how to contribute, either by
clon ing or by patch.

- Added section on contributing to the documentation and how to
improve it.

- Made minor changes on the code style and English.

- Enphatised the difference between the mailing list and announcement
lists.

Austin503/pyglet,cledio66/pyglet,Austin503/pyglet,google-code-export/pyglet,gdkar/pyglet,xshotD/pyglet,google-code-export/pyglet,gdkar/pyglet,qbektrix/pyglet,Alwnikrotikz/pyglet,gdkar/pyglet,cledio66/pyglet,xshotD/pyglet,odyaka341/pyglet,Alwnikrotikz/pyglet,Austin503/pyglet,Alwnikrotikz/pyglet,cledio66/pyglet,odyaka341/pyglet,xshotD/pyglet,cledio66/pyglet,shaileshgoogler/pyglet,cledio66/pyglet,Alwnikrotikz/pyglet,xshotD/pyglet,kmonsoor/pyglet,kmonsoor/pyglet,odyaka341/pyglet,qbektrix/pyglet,kmonsoor/pyglet,shaileshgoogler/pyglet,qbektrix/pyglet,arifgursel/pyglet,Austin503/pyglet,arifgursel/pyglet,arifgursel/pyglet,odyaka341/pyglet,arifgursel/pyglet,qbektrix/pyglet,gdkar/pyglet,arifgursel/pyglet,Austin503/pyglet,shaileshgoogler/pyglet,qbektrix/pyglet,odyaka341/pyglet,xshotD/pyglet,kmonsoor/pyglet,google-code-export/pyglet,gdkar/pyglet,google-code-export/pyglet,Alwnikrotikz/pyglet,shaileshgoogler/pyglet,google-code-export/pyglet,kmonsoor/pyglet,shaileshgoogler/pyglet